It is known that gaseous contaminants usually by deterioration can occur in the SF.sub.6 gas composition used as insulation in such appliances. In addition to humidity which finds its way into the insulating gas and is a pronounced problem contributing to the decomposition products of the sulfur hexafluoride (SF.sub.6), secondary reaction products of these decomposition products are formed with the substances present in the electrical appliance. These decomposition consequences are caused by electrical discharges, which in some cases occur in normal operation, as in switches, and in some cases only when a defect develops, as in transformers. The gaseous contaminants which occur as a result of decomposition of the SF.sub.6, i.e., the decomposition products themselves and their secondary reaction products, are undesirable since they attack the materials used in the appliance, and thus also impair the insulation, consequently endangering the reliability of the appliance. While analysis of SF.sub.6 gas samples taken from electrical equipment to determine the presence therein of SF.sub.6 decomposition products and their concentrations have been conducted in the past, the more reliable techniques have been limited to laboratory application. In such situations, the time which elapses between the time of collection of an SF.sub.6 sample from the field and the time when practical analysis in the laboratory can be effected has been shown to be important especially when dealing with very low concentrations of SF.sub.6 by-products.
Also while devices for monitoring decomposition products are known such as that of U.S. Pat. No. 3,512,939 and Japanese Patent Application Publication No. 47-11478, both of which rely on a color change in the instrument to signal the presence of SF.sub.6 decomposition products, no device is known which provides a simple and easy to use portable tool for use on the site that provides a reliable readout of the degree of SF.sub.6 decomposition products which are present in low levels in the SF.sub.6 insulating gas. For example, the device of the Japanese application can only detect SF.sub.6 decomposition products that result in forming fluorine or hydrogen fluoride reaction products. Also the sensitivity of that device is low due to the dependence on the presence of fluorine and hydrogen fluoride in the SF.sub.6 gas to provide a measurement.
It is, therefore, apparent that a need exists for a portable analyzer which detects, in situ, the level of SF.sub.6 gas decomposition products in operating electrical apparatus that use SF.sub.6 gas as an insulating medium to provide timely and reliable warning based on early detection of SF.sub.6 decomposition that the equipment should be serviced before costly breakdown occurs.